Among automobile body parts having a closed section frame, a windshield pillar (A pillar), a center pillar (B pillar), a rear pillar (C pillar), a wheel arch (tire housing) and a side sill may cause wind noise. Therefore, the closed section of such a part is usually filled with a foam for shutting out noises (an insulation wall).
For example, a prefoamed polyurethane foam is crammed into the closed section of an automobile body part by hands, or a shaped material of a heat-blowing injection composition is adhered to the inside surface of the closed section and then thermally foamed in a baking step. However, neither of these processes can be automated.
Then, as a injection composition suitable for an automated injecting process, an automatic injecting type paste form heat-blowing injection composition was developed. For example, as a injection composition which has an anti-stringy property during application, prevents sagging during thermal blowing and is foamed at a high expansion ratio, a composition is proposed, which comprises a liquid rubber (for decreasing a viscosity and imparting adherence to an oil-surface steel plate), an unvulcanized rubber (for increasing an expansion ratio by virtue of the high retention of expansion gas), a curing agent and a curing accelerator, a softening agent (for lubricating rubber particles), a blowing agent and a blowing aid, a flake-form inorganic filler (for preventing sag and improving an anti-stringy property), and a thixotropic agent (for preventing sag) (see JP-B-3017571). The composition disclosed in this patent specification is applied in the form of beads at specified sites of a panel and then cured in a foamed state by heating in a baking oven in a subsequent step of electrodeposition coating. The cured material exhibits good performances of soundproofing and shutting out wind noise.